Magnetic flux leakage above ground tank floor inspection devices (scanners) have been around for 20+ years. These devices use very strong magnets to saturate a section of a typically coated steel tank floor. This means the scanner is firmly held against the steel floor by the magnets with a force in hundreds of pounds.
The scanners are suspended away from the tank floor with four wheels. The wheels need to be pulled away from the tank floor and repositioned numerous times. This is typically accomplished by tilting the scanner back on the rear wheels using the leverage of a long handle. The rear wheels support much more than the weight of the inspection process. Then the scanner is moved to a new location and lowered to the tank floor. The scanner crashes against the tank floor because the strength of the magnetic field increases exponentially as it gets close to the tank floor. The front wheels need to absorb the crash force without changing the adjusted wheel height.
The wheel height needs to be different for different conditions like tank floor coating thickness, tank floor steel thickness, and wheel wear. In other words, the location of the wheels relative to the scanner body need to be adjusted. Existing inspection devices use some form of a screw or different sized wheels to set the wheel height.
The wheel height adjustment with a screw typically uses a screw to set the height and some clamping method to hold the position and keep forces from damaging the screw. There also needs to be some way to keep debris away from the screw threads. There are several scanners that use this adjustment technique but it is somewhat complex and has been prone to damage from operator errors.
Adjusting the wheel height with different sized wheels has multiple drawbacks: 1) the operator has to carry several sets of wheels for each height needed, 2) wheel wear changes the wheel height, and 3) the cost of having multiple wheels and having to replace them is expensive.
To this end, a need exists to allow the wheel height on a scanner to be adjusted and then easily resist the mechanical forces trying to change the wheel height during the inspection process of a tank floor. It is to such an assembly that the present disclosure is directed.